module Sinatra
  module MarkupPlugin
    module OutputHelpers
      # Captures the html from a block of template code for erb or haml
      # capture_html(&block) => "...html..."
      def capture_html(*args, &block)
        if self.respond_to?(:is_haml?) && is_haml?
          block_is_haml?(block) ? capture_haml(*args, &block) : block.call
        elsif has_erb_buffer?
          result_text = capture_erb(*args, &block)
          result_text.present? ? result_text : (block_given? && block.call(*args))
        else # theres no template to capture, invoke the block directly
          block.call(*args)
        end
      end

      # Outputs the given text to the templates buffer directly
      # concat_content("This will be output to the template buffer in erb or haml")
      def concat_content(text="")
        if self.respond_to?(:is_haml?) && is_haml?
          haml_concat(text)
        elsif has_erb_buffer?
          erb_concat(text)
        else # theres no template to concat, return the text directly
          text
        end
      end

      # Returns true if the block is from an ERB or HAML template; false otherwise.
      # Used to determine if html should be returned or concatted to view
      # block_is_template?(block)
      def block_is_template?(block)
        block && (block_is_erb?(block) || (self.respond_to?(:block_is_haml?) && block_is_haml?(block)))
      end

      # Capture a block of content to be rendered at a later time.
      # Your blocks can also receive values, which are passed to them by <tt>yield_content</tt>
      # content_for(:name) { ...content... }
      # content_for(:name) { |name| ...content... }
      def content_for(key, &block)
        content_blocks[key.to_sym] << block
      end

      # Render the captured content blocks for a given key.
      # You can also pass values to the content blocks by passing them
      # as arguments after the key.
      # yield_content :include
      # yield_content :head, "param1", "param2"
      def yield_content(key, *args)
        content_blocks[key.to_sym].map { |content|
          capture_html(*args, &content)
        }.join
      end

      protected

      # Retrieves content_blocks stored by content_for or within yield_content
      # content_blocks[:name] => ['...', '...']
      def content_blocks
        @content_blocks ||= Hash.new {|h,k| h[k] = [] }
      end

      # Used to capture the html from a block of erb code
      # capture_erb(&block) => '...html...'
      def capture_erb(*args, &block)
        erb_with_output_buffer { block_given? && block.call(*args) }
      end

      # Concats directly to an erb template
      # erb_concat("Direct to buffer")
      def erb_concat(text)
        @_out_buf << text if has_erb_buffer?
      end

      # Returns true if an erb buffer is detected
      # has_erb_buffer? => true
      def has_erb_buffer?
        !@_out_buf.nil?
      end

      # Used to determine if a block is called from ERB.
      # NOTE: This doesn't actually work yet because the variable __in_erb_template
      # hasn't been defined in ERB. We need to find a way to fix this.
      def block_is_erb?(block)
        has_erb_buffer? || block && eval('defined? __in_erb_template', block)
      end

      # Used to direct the buffer for the erb capture
      def erb_with_output_buffer(buf = '') #:nodoc:
        @_out_buf, old_buffer = buf, @_out_buf
        yield
        @_out_buf
      ensure
        @_out_buf = old_buffer
      end
    end
  end
end